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Full text of "The manufacture and properties of iron and steel"

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INFLUENCE OF HOT WORKING ON STEEL.                    263
ered to some extent. The reduction of area is also irregular, but it seems to be independent of the thickness even in the thinnest plate. The conclusion seems justifiable that if the billets have already received sufficient work, the good condition caused thereby is not destroyed by reheating, since bars rolled from them reach their standard level of quality with only a reasonable degree of reduction, as proven by the fact that further work gives no decided improvement. But it is also certain, as shown by all experience, that no harm can" be done by increased work, and that there is a slight gain in the long run provided the finishing temperature remains constant.
SEC. XlVd.—Experiments 'on forgings.—-The persistency of a proper structure even through subsequent heating may be seen in Table XIV-E, which gives the results obtained from a series of .forged billets. The original bloom was 6 inches square, being rolled from an ingot 18"x20". From this bloom several short pieces were cut and treated in different ways:
A was not reheated, but a test-piece was cut from it as a standard of'comparison.
B was heated to a full working heat and cooled without hammering.
C was hammered to 5 inches square in one heat,
D was hammered to 4 inches square in one heat.
IS was hammered to 3 inches square in one heat.
F was hammered to 2: inche^ square in one heat.'      •
G was homered to j2 inches square in one heat from the annealed bar IB and was finished! at a cherry Ted heat, j
H was hammered to 5 inches square, then reheated and hammered to 4 inches.            , .
I was hammered to 4 inches square, then reheated and hammered to 3 inches.
K was hammered to 3 inches square, then reheated and hammered to 2 inches.
L was hammered to 5 inches square, then overheated and cooled without hammering..............
M was made by reheating the burned piece L and hammering to '% inches square in one heat, being finished at a cherry red heat.
All the pieces were worked under a 4-ton double-acting hammer, and the test-bars were cut from the corner of the billet and pulled in a length of 2 inches.               . . .. ........